Objective: To understand the cognition and attitudes of men who have sex with men (MSM) towards HIV testing and explore in-depth reasons preventing them from testing. Methods: The function of "opinion" in Blued, a gay geo-social networking application (GSN), was adopted to collect qualitative data of ideas and attitudes towards HIV testing of the users between December 2017 and January 2018. The data was analyzed based on grounded theory approach. Results: 28 269 Blued users participated in the activity and 1 977 posted comments. Four key themes were identified, i.e. no/low risk of contracting HIV, stigmatization of HIV testing, long-term relationship and conventional impediments of HIV testing. Conclusion The cognition and attitudes of the target population derived from the analysis of "opinion" function in Blued, such as the stigmatization of the behavior of HIV testing influencing the attitude of HIV testing, could help researchers build a more accurate detection and promotion strategy instead of a very general intervention on the public.

{L-End}Objective To analyze the spectrum characteristics of noise hazards in the metal products industry. {L-End}Methods A total of six metal product industries were selected as research subjects using stratified sampling method. The noise intensity (A/C-weighted) and noise spectrum (Z-weighted) of workplaces and job positions were detected. The characteristics of the noise spectrum of each job position were analyzed using the difference between equivalent continuous C-weighted sound pressure level (L_Ceq)-equivalent continuous A-weighted sound pressure level (L_Aeq), the dominant frequency of the noise spectrum, and cluster analysis methods. {L-End}Results The workplace noise and job position noise of 11 main noise positions in the metal products industry were exceeded national standard, with incidence of 69.2% and 78.1%, respectively. The average of normalization of equivalent continuous A-weighted sound pressure level to a normal 40 hours working week exceeded the national standard in 100.0% of hydraulic workers, welders, and ultrasonic cleaning workers. The result of spectrum analysis showed that the noise in the metal product industry was mainly broadband. The noise of the collision welder position was classified as low-frequency broadband noise, while the noise of the painter position was classified as low-frequency narrowband noise. The noise spectrum characteristics of other positions were similar and classified into one category, all of which were broadband noise. Among them, numerical control lathe workers, welders, threaders, machinists, and cutters were exposed to high-frequency broadband noise, while press workers were exposed to mid-frequency broadband noise, and grinders, hydraulic workers, and ultrasonic cleaning workers were exposed to low-frequency broadband noise. The detection rate of binaural high-frequency hearing threshold improvement among workers was 61.7%, and there was no statistical correlation between the detection rate of binaural high-frequency hearing threshold improvement and the noise level intensity of each spectrum. {L-End}Conclusion The level of noise hazards in the metal products industry is severe. Effective engineering control measures and hearing protection measures should be implemented based on the spectral characteristics of noises.

Objective: To assess risk of HIV infection and its risk factors among men who have sex with men (MSM) in Beijing, China. Methods: We conducted a cross-sectional online survey in October, 2017. Inclusion criteria of participants were: aged 18 year or more; resided in Beijing; conducted homosexual activities in past six months; self-reported HIV status as negative or unclear. Demographic information, HIV test history, social media use, and high-risk sexual behaviors were collected by a self-reporting questionnaire, and a HIV risk assessment tool was used to assess HIV risk of MSM, 5 388 particpants were finally enrolled in the study. Logistic regression model was used to analyze factors associated with risk of HIV infection. Results: Of the total 5 388 participants, most were 18-29 years old (64.35%), and the proportion of medium and high HIV risk score was 40.36%. The odds of medium and high HIV risk score among MSM who logged onto the app 1-20 times per week and>20 times per week were higher comparing with those who logged onto the app<1 time per week (OR=1.22, 95%CI: 1.02-1.46; OR=1.69, 95%CI: 1.38-2.06, respectively); MSM who completed college or higher education had lower probability of medium and high HIV infection risk, comparing with those who only had high school education level (OR=1.25, 95%CI:1.09-1.43) or junior or below education level (OR: 1.27, 95%CI: 1.05-1.53); MSM who did not conduct HIV test in past year had lower risk of medium and high HIV infection risk comparing with MSM who conducted HIV test in past year (OR=0.87, 95%CI: 0.77-0.99), and those who reported their HIV infection status unclear had higher probability of medium and high HIV infection risk than MSM who reported their HIV infection status negative (OR: 1.63, 95%CI: 1.44-1.86). Conclusion The proportion of MSM who were in medium and high HIV infection risk score was high in Beijing. Lower level of education, high frequency of social media use, conducted HIV test in past year, and unclear of their own HIV infection status were associated with medium and high level of HIV infection risk.

Objective: To investigate the related factors of unprotected sexual behaviors among male students who have sex with men in Beijing. Methods: Male students who have sex with men were recruited from May 2018 to July 2018 at two voluntary counseling and testing (VCT) clinics in Beijing by convenient sampling method. Information being collected during in-depth personal interviews with a semi-structured outline included ways to seek sexual partners, sexual partners characteristics, attitude of condom use, incidence and causes of unprotected sexual behaviors, rush poppers and alcohol use. The text information was summarized and analyzed by Nvivo 11.0 software. Results: A total of 35 male students who have sex with men were recruited and interviewed, the median of age was 22 years old (P₂₅-P₇₅: 21-24 years old). We found that incomprehensive knowledge of condom use, low risk perception of non-anal sexual behaviors, rush poppers and alcohol use were risk factors of unprotected sexual behaviors on individual level. Besides, sex with regular sex partners, partners who were much older or not from campus, and insertive partners are more likely to be unprotected. Furthermore, refusal of condom use by sexual partners and low self-efficacy of decision-making on condom use were the main reasons for unprotected sexual behaviors among male student who have sex with men. Conclusion Lack of condom use knowledge, low risk perception of non-anal sexual behaviors and insufficient ability to refuse non-condom requirements for regular sex partners, partners who were much older or not from campus, and insertive partners are related factors of unprotected sexual behaviors among male students who have sex with men.

Objective: To understand the prevalence of facility-based HIV testing and its associated factors among men who have sex with men (MSM) in Beijing city. Methods: An application-based cross-sectional survey was employed to understand HIV site test situation and associated factors. The survey was carried out from May 14^th to 21^st, 2016. Users of a smart phone application for gay dating were recruited and those eligible for this survey were investigated with an online self-administered questionnaire. Information of demographics, sexual behaviors, facility-based HIV testing history and recreational drug abuses were collected. The multivariate logistic regression was used to make comparison among different groups and assess associated factors. Results: A total of 7 494 participants were enrolled in the survey with mean age of (28.81 ± 7.38) years, 87.14% (6 530/7 494) sought sexual partners through internet. The proportion of facility-based HIV testing in 1 year was 42.55% (3 189/7 494), MSM who were 25-29 years had higher proportion of facility-based HIV testing in 1 year, the proportion was 45.56%(1 104/2 423). Among MSM who could insist in using condom during anal sex (50.46% (1 539/3 050)), the proportion of HIV site testing in 1 year was higher. The MSM who reported seeking healthcare for symptoms of a sexually transmitted infections (STIs) in the past year or ever using recreational drug had higher proportion of facility-based HIV testing, the proportions were 56.81% (409/720) and 52.00% (1 340/4 917), respectively. Compared with alone cohabitation, cohabitating was associated with decreased odds of HIV facility-based testing in past 1 year(odds ratio (OR)= 0.79, P<0.001). Compared with homosexual sexual orientation, bisexual sexual orientation was associated with decreased odds of facility-based HIV testing (OR=0.83, P=0.004). With the increasing of number of male anal sex partners, the odds of HIV facility-based testing was increasing (OR=1.31, P<0.001) But with the decreasing of the frequency of condom using with male anal sex partners, the odds of facility-based HIV testing was decreasing (OR=0.85, P=0.014). Using recreational drugs (OR=1.36, P<0.001) and seeking healthcare for symptoms of a STI in the past 1 year (OR=1.73, P<0.001) were associated with decreased odds of HIV site testing. Conclusion MSM in Beijing had lower proportion of facility-based HIV testing in past 1 year. Multiple anal sex partners, using recreational drugs, seeking healthcare for symptoms of a STI in the past year, cohabitating, bisexual sexual orientation, and lower frequency of condom using with male anal sex partners were associated with the odds of HIV facility-based testing in past 1 year.

Objective:To investigate the protection of Active Breathing Coordinator(ABC)technique for heart and its substructures in radiotherapy for left breast cancer.Methods:A total of 50 patients with left breast cancer who underwent radiotherapy in our department were retrospectively selected,and treatment plans with intensity modulated radiotherapy(IMRT)were designed on the images of ABC combined with deep inspiration breath hold(ABC-DIBH)computed tomography(CT)and free-breathing(FB)CT,respectively.The dose parameters of the organ at risks(OARs)of heart and its substructures,including left ventricle(LV),left atrium(LA),right ventricle(RV),right atrium(RA),left main coronary artery(LMCA),left anterior descending coronary artery(LAD),left circumflex coronary artery(LCX)and right coronary artery(RCA),were compared between the two conditions.Results:Compared with FB,the dose of 2%volume(D2),the mean dose(Dmean),the percent volumes covered by different doses(V30,V20,V10,V5)decreased respectively 32.91%(absolute reduction of 1279.11 cGy),36.12%(195.94cGy),58.95%(2.8%),54.32%(3.58%),50.14%(5.56%)and 46.22%(9.67%)of heart under ABC-DIBH condition,and the differences were significant(t=10.28,12.81,9.16,10.28,12.82,12.24,P＜0.01),respectively.In addition,the Dmean values of LV,LA,RV,RA,LMCA,LAD,LCX and RCA decreased by 37.64%(absolute reduction was 285.92 cGy),15.38%(23.68 cGy),34.12%(118.93cGy),9.72%(12.52 cGy),22.17%(47.99 cGy),31.81%(820.63 cGy),16.51%(34.72 cGy)and 14.86%(34.11cGy)under ABC-DIBH condition,respectively,the differences were significant(t=9.50,3.71,6.20,8.65,3.18,10.92,4.26,6.71,P＜0.05).Conclusion:ABC technique can greatly reduce the received doses of heart and its substructures by extending the distance between the heart and the target region with DIBH,thus can form a very effective protection for the heart and its substructures.In addition,it can eliminate the dynamic variation of target location of breast cancer caused by respiratory,and avoid a series of problems,such as target missing,overexposure on normal tissue,and dose deviation.

Objective:To compare the dosimetric differences between active breathing coordinator (ABC) and Catalyst for respiratory gating after breast conserving surgery for left breast cancer.Methods:Data of 48 female patients with left breast cancer after breast conserving surgery admitted to the Radiotherapy Department of Shenzhen People′s Hospital from November 2020 to August 2021 were retrospectively selected. They were randomized to receive dynamic intensity modulated radiotherapy (IMRT) plans with ABC or Catalyst. The dosimetric differences in targets and organs at risk between the two groups were analyzed.Results:Comparison of the two respiratory gating IMRT plans revealed no statistically significant differences ( P > 0.05) in D90%, D98%, Dmax, Dmean, conformity index (CI), homogeneity index (HI), and monitor unit parameters in the target volume, (i.e., chest wall), as well as the ipsilateral lung and heart under the deep inhalation breath hold (DIBH) mode. The Dmean, Dmax, and D2% of the left anterior descending coronary artery (LAD) in the Catalyst group were better than those in the ABC group [(1 047.72 ± 1 401.84) vs. (454.48 ± 206.26), (1 619.28 ± 809.05) vs.(1 068.53 ± 419.63), (1 405.85 ± 798.30) vs. (1 016.54 ± 592.00) cGy], with statistically significant differences ( t= -2.07, -3.18, -2.07, P<0.05). Conclusions:Both ABC and Catalyst respiratory gating systems meet the requirements for clinical treatment, with the latter more effective in reducing the exposure dose of LAD.

Objective:To study the impact of the Varian real-time position management (RPM) respiratory gating system on radiotherapy planning dosimetry.Methods:The radiotherapy plans of 40 cases with thoracic or abdominal tumors were retrospectively selected in this study. The motion phantom for quality control was adopted to generate respiratory gating signals, and the 30%-60% stable phase at the end of expiratory was selected as the respiratory gating window. The dose verification for the abovementioned radiotherapy plans was performed using the Portal Dosimetry (PD) system under RPM respiratory gating mode with the Edge accelerator. Afterwards, dose analysis was performed with different γ passing rate criteria and the distribution characteristics of γ values were analyzed. Finally, the verification results between the non-gating mode and the gating mode were compared.Results:Under the respiratory gating mode, the passing rates of all intensity-modulated radiation therapy/volumetric-modulated arc therapy (IMRT/VMAT) plans with or without flattening filters were over 95.5% by γ criteria of (3%, 3 mm) or (3%, 2 mm) and were over 90% by stricter γ criteria of (2%, 2 mm). All plans met the clinical requirements recommended by the American Association of Physicists in Medicine (AAPM). The passing rates of dose verification under non-gating mode were slightly better than those under respiratory gating mode, and the differences between the two modes were statistically significant (3%/3 mm, Z =-1.45; 3%/2 mm, Z =-2.86; 2%/2 mm, Z =-3.70; 1%/1 mm, Z =-4.52; P<0.05). There was no significant difference in the minimum and maximum values of γ and the share of γ > 1.5 of plan verification result under the two modes. However, the average value and standard deviation of the γ were generally smaller under the non-gating mode. Conclusions:The impact of the introduction of RPM respiratory gating technology on dose is clinically acceptable, and the execution of these plans in this gating mode is safe and reliable.

Objective:To compare translational and rotational setup errors between immobilization with open masks combined with positioning with the optical surface monitoring system (OSMS) and immobilization with full masks combined with positioning with laser lights and mask markers, find the advantages of open masks combined with OSMS in hypofractionated stereotactic radiotherapy (HSRT) for brain metastases, and calculate planning target volume (PTV) expansions with different immobilization and positioning method for patients with brain metastases.Methods:The setup data of 55 patients with brain metastases who received HSRT were analyzed retrospectively. According to immobilization and positioning method, the patients were divided into group A (OSMS + open masks), group B1 (full head-neck-shoulders masks + polyurethane foam cushions), and group B2 (full head-neck-shoulders masks + standard headrests). Positioning was directed by automatic couch motion in OSMS in group A and by laser lights and mask markers in groups B1 and B2. Cone beam computed tomography (CBCT) scans were registered using the bone registration method to obtain setup errors in six directions ( x, y, z, roll, pitch, yaw). PTV expansions were calculated according to the van Herk formula. Results:A total of 288 sets of CBCT registration data were acquired. Among three groups, group A showed the smallest mean setup errors and 3D vector error, which were (0.47±0.33) mm, (0.49±0.31) mm, (0.44±0.31) mm, (0.42±0.32)°, (0.48±0.31)°, (0.42±0.22)°, and (0.90±0.39) mm, respectively. Group A differed significantly from group B1 and group B2 in the errors at all directions ( P < 0.05) except for the yaw direction compared with group B1 ( P > 0.05). Group A had no setup error ≥2 mm in translational directions or ≥2° in rotational directions. Group B1 showed significantly smaller setup errors in the y, z, and yaw directions and 3D vector error than group B2 ( P < 0.05). In group A, PTV expansions in three directions ( x, y, and z) were 1.32, 1.19, and 1.22 mm, respectively, which were smaller than those of the other two groups. Conclusions:In HSRT for patient with brain metastases, compared with full head-neck-shoulders masks combined with laser lights and mask markers, open masks combined with OSMS can significantly improve setup precision in six directions and reduce repeated setup and PTV expansions, which shows promise for clinical application.